The present invention relates to electroacoustic transducers. More particularly, it relates to an angular postion sensor for a scanning electroacoustic transducer.
In the art of medical diagnostics, one form of non-invasive examination of the internal organs of a body under examination involves the use of ultrasonic transducers. These transducers are frequently mounted within a housing filled with an inert liquid and arranged to oscillate in an angularly scanning motion. The housing is generally relatively opaque to the ultrasonic pulses generated by the transducer, with the exception of a relatively transparent window or diaphragm, in the operating end of the housing structure. The transducer is positioned and oscillated to direct the acoustic pulses through the diaphragm, or window, into the body under examination. The acoustic pulses transmitted into that body are then reflected back toward the transducer by interfaces of tissue within the body, to produce electrical pulses which may be translated into an image of the interior of the body being examined.
In order for those pulses to be translated into an image of the interior of the body, it is essential that the scanning of the transducer be synchronized with the display apparatus. While it is possible to derive a synchronizing signal from the control signal driving the oscillating mechanism. In theory, such a signal should be representative of the position of the transducer, in practice, however, the resulting signal may be significantly out of sync with the position of the transducer. Again, the position indicating signal may be derived from an electrical signal generator mechanically coupled to the oscillatory members. Such structure would tend to unduly load the oscillatory structure and, being mechanical in nature, would tend to rapidly wear out.